Data from: The Phylogeny of the Diploporita: a polyphyletic assemblage of blastozoan echinoderms

The phylogenetic relationships of Paleozoic blastozoan echinoderms are
poorly understood and many of the traditionally ascribed groups are likely
polyphyletic. Diploporitans, those blastozoans with double pore
(diplopore) respiratory structures, have never been placed within a
rigorous phylogenetic framework and their highly variable morphologies
suggest that they do not represent a natural clade. A maximum parsimony
phylogenetic analysis, spanning a wide range of diploporitan and related
taxa, indicates that diplopore-bearing blastozoans are a polyphyletic
grouping and, consequently, that diplopore respiratory structures have
evolved more than once within the echinoderms. A constraint analyses
indicate that a single diplopore-bearing clade bearing the traditionally
defined Glyptosphaeritida, Sphaeronitida, Asteroblastida is less
parsimonious than multiple diplopore-bearing clades inferred by the
unconstrained analysis.